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HelpTest ID DHRF Dihydrorhodamine Flow Cytometric N-Formyl-Methionyl-Leucyl-Phenylalanine Test, Blood
Useful For
Evaluation of RAC2 deficiency and RAC2 gain of function
Reporting Name
DHR Flow fMLP, BSpecimen Type
WB Sodium HeparinShipping Instructions
Specimens are required to be received in the laboratory weekdays and by 4 p.m. on Friday. Collect and package specimen as close to shipping time as possible. Ship specimen overnight in an Ambient Shipping Box-Critical Specimens Only (T668) following the instructions in the mailer.
It is recommended that specimens arrive within 24 hours of collection.
Samples arriving on the weekend and observed holidays may be canceled.
Necessary Information
Ordering physician name and phone number are required.
Specimen Required
Both a whole blood sodium heparin specimen and a whole blood sodium heparin control specimen from an unrelated, healthy donor are required.
Supplies: Ambient Shipping Box-Critical Specimens Only (T668)
Patient:
Container/Tube: Green top (sodium heparin)
Specimen Volume: 5 mL
Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.
Normal Control:
Container/Tube: Green top (sodium heparin)
Specimen Volume: 5 mL
Collection Instructions:
1. Collect a control specimen from a normal (healthy), unrelated person within an hour of the patient's specimen collection time.
2. Label clearly on outermost label normal control.
3. Send whole blood specimen in original tube. Do not aliquot.
Specimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| WB Sodium Heparin | Ambient | 48 hours | GREEN TOP/HEP |
Clinical Information
This assay can be used for the diagnostic evaluation of RAC2 deficiency, which is a neutrophil defect that causes profound neutrophil dysfunction with decreased chemotaxis, polarization, superoxide anion production, azurophilic granule secretion. This disease is caused by inhibitory variants in the RAC2 gene, which encodes a Rho family GTPase essential to neutrophil activation and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase function.(1) Patients with RAC2 deficiency have been shown to have normal neutrophil oxidative burst when stimulated with phorbol myristate acetate (PMA), indicating normal NADPH oxidase activity, but abnormal neutrophil responses to N-formyl-methionyl-leucyl-phenylalanine (fMLP), which is a physiological activator of neutrophils. The defective oxidative burst to fMLP, but not to PMA, is consistent with RAC2 deficiency.(2) By contrast, gain of function variants in RAC2 would lead to a an exaggerated response to fMLP.(3)
Reference Values
|
Result name |
Unit |
Cutoff for defining normal |
|
% fMLP ox-DHR+ |
% |
≥10% |
|
MFI fMLP ox-DHR+ |
MFI |
≥2 |
|
Control % fMLP ox-DHR+ |
% |
≥10% |
|
Control MFI fMLP ox-DHR+ |
MFI |
≥2 |
fMLP = N-formyl-methionyl-leucyl-phenylalanine
DHR = dihydrorhodamine
MFI = mean fluorescence intensity
The appropriate age-related reference values for Absolute Neutrophil Count will be provided on the report.
Interpretation
An interpretive report will be provided, in addition to the quantitative values described in Clinical Information.
Interpretation of the results of the quantitative dihydrorhodamine (DHR) flow cytometric assay has to include both the proportion of positive neutrophils for DHR after N-formyl-methionyl-leucyl-phenylalanine stimulation, and the mean fluorescence intensity.
Clinical Reference
1. Ambruso DR, Knall C, Abell AN, et al: Human neutrophil immunodeficiency syndrome is associated with an inhibitory Rac2 mutation. Proc Natl Acad Sci U S A. 2000 Apr 25;97(9):4654-4659
2. Accetta D, Syverson G, Bonacci B, et al: Human phagocyte defect caused by a RAC2 mutation detected by means of neonatal screening for T cell lymphopenia. J Allergy Clin Immunol. 2011 Feb;127(2):535-538
3. Hsu AP, Donko A, Arrington ME, et al: Dominant activating RAC2 mutation with lymphopenia, immunodeficiency, and cytoskeletal defects. Blood. 2019 May 2;133(18):1977-1988
Report Available
3 to 4 daysTest Classification
This test was developed using an analyte specific reagent. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
86352
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| DHRF | DHR Flow fMLP, B | 98123-3 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| ANC | Absolute Neutrophil Count | 751-8 |
| FMPPP | % FMLP ox-DHR+ | 85373-9 |
| FMPM | MFI fMLP ox-DHR+ | 85370-5 |
| ANCC | Control Absolute Neutrophil Count | 85369-7 |
| FMPPC | Control % fMLP ox-DHR+ | 85372-1 |
| FMPMC | Control MFI fMLP ox-DHR+ | 85371-3 |
| DHRFI | Interpretation | 69052-9 |
Method Name
Flow Cytometry